Personally I think there are no absolutes to this, and that it depends upon the individual and physique.
Following the current scare mongering advice, I would end up carrying far more weight in water than I need to somewhat decreasing the object
Yes my urine does sometimes get somewhat dark, yes I do sweat like the proverbial pig, but I have survived these fifty odd years without dehydration nonetheless.
By that same definition then smoking is neither dangerous or bad for your health as some ones uncle somewhere smoked for 50 years without any problems.
Your body your choice, but to label the so far excellent advice as
scaremongering is both incorrect and irresponsible.
Every drop of fluid your body exudes NEEDS to be replaced, be that sweating, breathing or if you have a poorly tummy.
Yes you can SURVIVE with a lower fluid intake for short periods, but it will take a toll on both your performance, ability and in extreme cases your organs.
For some of your age your body is not as resistant or strong as it was when you were younger, you can't "get away" with things at 50+ years that you did when you were 20.
Personally i would recommend you do some reading and re-evaluate your opinion as you are wrong and at your age you need to take better care of yourself to help avoid future problems.
Some good reading here:
http://www.mayoclinic.com/health/dehydration/DS00561/DSECTION=risk-factors
Of particular interest:
Older adults.
As you age, you become more susceptible to dehydration for several reasons:
Your body's ability to conserve water is reduced, your thirst sense becomes less acute and you're less able to respond to changes in temperature.
What's more, older adults, especially people in nursing homes or living alone, tend to eat less than younger people do and sometimes may forget to eat or drink altogether. Disability or neglect also may prevent them from being well nourished. These problems are compounded by chronic illnesses such as diabetes, by hormonal changes associated with menopause and by the use of certain medications.
